Project 2: It is proposed to study abnormalities of GH and IGF structure and action. In Subproject 1 we will correlate abnormalities of serum GH binding protein with those of the GH receptor on liver membrane using a model of severe growth retardation, i.e. the micro-Yucatan pig. We will continue our studies of the serum GH-binding protein in the serum of short children. A GH-BP from a very short child, which is significantly larger than normal by gel permeation, will be purified by affinity chromatography and its SDS-PAGE migration before and after N-glycanase treatment determined. We have found patients with apparent GH resistance and absence of GH-BP in their serum as detected by 125I GH binding who retain GH- receptor immunoreactivity on fibroblasts. We will test these fibroblasts for specific binding of 125I GH binding. We will characterize the membrane endopeptidase which is responsible for shedding of GH binding protein by IM-9 lymphocytes and by so doing gain insight into the mechanism by which the binding protein arises in human beings. In Subproject 2 we will focus on abnormalities of IGF structure with major attention given to overproduction of IGF-II and its significance in non-islet cell tumor hypoglycemia. We will extend our observations of the abnormal serum binding of IGF-II peptides in this condition and investigate the reason for the virtual absence of the 150 kD IGF-II binding protein complex in this condition. In Subproject 3 we will investigate the mechanism of IGF-I insensitivity of certain fibroblast strains which we have isolated from short children. The contribution of IGF binding proteins secreted into the medium and those BPs which remain cell associated will be differentiated. We will study the relative importance of individual binding proteins in decreasing IGF-I action. In these studies, extensive use will be made of IGF-I variants produced by recombinant methods which have selective affinities for IGF-I receptors or IGF-I binding proteins.